The 275 Men Accommodation Barge was the first DP2 vessel to be built in India. The hallmark of the design was its simplicity – very simple but unorthodox concept to tackle a complex problem.
Many heads came together for the project.
It took 2 years for completion, from order placement to delivery.
The 275 Men Accommodation Barge
Before satellite technology took over, communication across the world was through cables. There are a large number of cables running on sea beds. Close to ports, the sea is well charted via hydrographic surveys and it is possible to designate an anchoring area which is free of sub-sea cables.
Problem comes offshore areas where oil production platforms (rigs) are located. Many vessels are required to service platforms rigs, to carry equipment and provisions, for anchor handling duties, for laying and/or repairing sub-sea piping, etc. To eliminate chances of collision with and damage to rigs, supply vessels and are discouraged from going alongside offshore platforms. But they need to be stationary and close to platforms. Dropping anchors is often not allowed as it may damage the sub-sea cables, in case they are located in that area.
The solution was dynamic positioning (DP). DP was achieved by adjusting the power output and direction of ships main propellers as well as bow and/or stern thrusters. A sensor driven DP software receiving continuous inputs speed/direction of wind and current, computes the best possible combination of power and direction of the propellers and thrusters which will counter wind and current and keep the vessel positioned at one place.
The problem in this case, the 275 Men Accommodation Barge was that it was a square platform and non-propelled. The inboard power generation was primarily for normal ship services. Most of the time the vessel will be anchored at some safe location. It was impractical to use inboard power just for very infrequent DP requirement. The required power will be abnormally high and wasted for most of the time.
An out-of-the-box design was conceived and used – perhaps resulting in a first off design where DP had no connection to the main power supply. Four thrusters in the four compartments at four corners of the barge were installed and each was independently driven by its own prime mover and each DP compartments was totally self-sufficient and did not in any way depend on normal systems of the vessel.
The DP2 system
A simple and most widely used DP installation is DP1 where a failure of any one component of the system will make DP inactive. Many vessels were built in India. DP2 is a more sophisticated system where DP will keep functioning even in case of failure of any one component. And that can be a major break down of a power source or just a minor breakdown of a small pump.
Design: Navnautik Engineering
Builder: Shoft Shipyard Pvt Ltd
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